Traditionally, direct diagnosis of tuberculosis relies on microbiological techniques such as microscopic examination (relatively fast but of low sensitivity) and on culture isolation which, in addition to being labor-intensive, requires an extended incubation period. Currently there exist new methods for a faster detection of mycobacteria but they are too expensive to be used in developing countries. In the field of Molecular Biology, the methods require a high-complexity laboratory as well as trained personnel. Further, detection of mycobacterial DNA does not allow for distinguishing metabolically active bacteria from dead bacteria. In addition, it is a test of limited diagnostic use not only because it is prone to contamination at a technical level, but also because its use is limited to smear-positive respiratory specimens.
Worldwide, tuberculosis is considered as a re-emerging disease that remains a serious public health problem in many high prevalence countries. According to the World Health Organization, an important part of the world population has been in contact with the tuberculous bacillus and could potentially suffer from the disease over the next years (World Health Organization, Report on the tuberculosis epidemia, Geneve, Switzerland, World Health Organization; 1996). It has been estimated that around 8 million people are infected each year, of which 3 million actually develop the disease.